1. Field of the Invention
The present invention relates to an image recording apparatus for feeding sheets of paper using feed means.
2. Related Background Art
An image recording apparatus conventionally is provided with a built-in paper feeder, an option paper feeder (for feeding envelopes, postcards and the like) detachable from the image recording apparatus, and an option paper feed sensor for detecting recording paper on a conveying passage extending from the option paper feeder to the built-in paper feeder. In the case where recording paper fed from the option paper feeder is fed via the built-in paper feeder to a recording unit of the apparatus if the option paper feed sensor is still detecting the paper after a predetermined period of time has passed since a starting timing of the built-in paper feeder, then the apparatus determines that a paper jam has occurred. Then a process of dealing with jamming is performed.
However, such apparatus has the following drawbacks because a paper jam is detected even when multiple sheets of paper double fed from the option paper feeder are separated by the built-in feeder, with one sheet remaining behind the other.
(1) Even when the remaining sheet of paper can be fed regularly by the built-in paper feeder and set for normal printing, the operator must go through a process of removing the remaining sheet of paper to release the jamming condition.
(2) When jamming is detected because of the remaining sheet of paper while the printing of the preceding paper is in progress, a process of reprinting the same picture is needed as printing is interrupted at that point of time.
(3) When jamming is detected because of the remaining sheet of paper while the printing of the preceding paper is in progress, the paper being put into print is wasted and besides the remaining sheet of paper may be made unusable again at the time it is removed from the feeder.
(4) As the external paper feeder must be provided with a stack feed preventive function to obviate the foregoing shortcomings (1)-(3), the system tends to become complicated in configuration and costly.
Especially when a built-in paper feed mechanism is equipped with an effective stacked sheet separating function, the remaining sheet of double fed paper may properly be fed in most cases. As a result, the aforementioned problems (1)-(3) are highlighted and as to (4), both the external paper feeder and the built-in paper feed mechanism are each provided with such functions similar to each other, which also involves waste.